Understanding the mechanisms which allow for the maintenance of diverse communities is one of the central focuses of ecology. Recent work suggests that complex interactions such as trait-mediated indirect interactions (TMII), and more generally higher-order interactions, may play an important role in structuring ecological communities. Here we use a well-studied system of arboreal ants in coffee agroecosystems to empirically explore the role of TMII in structuring this community. We use, Azteca sericeasur, a dominant arboreal ant which excludes other ants from occupying coffee bushes near the trees it nests in. Prior work in the system has established the TMII between A. sericeasur and its specialist Pseudacteon parasitoid and that parasitoid pressure, thus TMII, is far greater on younger nests than older nests. Here we ask how varying strengths of TMII/parasitoid pressure influence the community of ants associated with A. sericeasur nests. We surveyed Azteca nests of varying ages to understand the influence of the parasitoids on the structure the arboreal ant community in space and through time.
Results/Conclusions
Our results show that young A. sericeasur nests with higher density of parasitoids and thus stronger TMII present little variation in the number of different ant species as we move away from the focal nest. This contrasts with older nests with weaker TMII, where arboreal ant species accumulate rapidly as we move away from the focal nest. We find higher richness closer to A. sericeasur nests with strong TMII than with weak TMII. This provides general support for the idea TMIIs may play an important role to reducing competitive exclusion. Interestingly, we find that older nests (weak TMII) have higher species richness as at the site level than the younger nests (strong TMII). These contrasting results highlight the importance of the spatial component of species interactions in our system. While at one scale we found sites with lower TMII have higher richness, but when we look at how this plays out in space we see that this is due to rapid accumulation of species as we move away from the focal nest. Our results suggest potential support for recent theoretical insights regarding the role of TMIIs but highlight the importance of considering space to further our understanding of these systems.